science

Question 1

energy flow in an ecosystem

Answer 1

Energy in an ecosystem flows from the producers through the food chain/web to the primary and secondary consumers.
Energy is used for MRSGREN. Around 10% of energy is used for growth and stored as chemical potential energy so 10% gets transferred up to the next trophic level. Because of this loss of energy at each trophic level there is not enough
energy in the food chain to support anymore than 5 trophic levels.

Question 2

Outline the basic process of bacteria (binary fission) and fungi
reproduction

Answer 2

1. The chromosome/DNA replicates (copies itself)
2. The cell membrane pinches the cytoplasm in half
3. The bacteria divides into two

Some hyphae grow upwards and produce swellings at their tips called sporangia
Spores form in the sporangia
The sporangia burst releasing the spores
Spores that land on a food source with moisture will germinate and grow hyphae which spread throughout the food

Question 3

Culture and observe bacteria and fungal population

Answer 3

Bacteria and Fungi can be cultured on agar plates.
A control dish is an unopened petri dish that is used to ensure the plates are sterile before adding bacteria or fungi.
Plates are sealed with tape because they contain millions of bacteria and fungi that are very harmful.
Plates are incubated upside down because condensation will form as they are being incubated and The water droplets carry microbes that could leak out which may be dangerous.
Plates are incubated at 25 degrees or below because we do not want to culture human bacteria
Colonies of bacteria look like greasy, shiny, smooth spots.
Colonies of fungi look like furry, fluffy, thread-like growths.

Question 4

Independent variable
Dependent variable
Controlled variables

Answer 4

the variable that is changed
the variable that is measured
the variables that are kept the same

Question 4

define energy

Answer 4

ability to do work

Question 5

Active energy

Potential energy

Answer 5

Active energy is energy that can cause movement either of waves, particles or objects

Potential energy is stored energy that can be turned into active energy

Question 6

Describe the law of energy conservation.

Answer 6

The law of conservation of energy says that energy cannot be created or destroyed, it can only be
transformed or transferred.

Question 7

Define energy efficiency

Answer 7

No energy transformation is 100% efficient. Energy Efficiency is how much of the input energy is
transformed to a useful form in percentage

Question 8

Define a wave

Answer 8

Waves transfer energy without transferring matter

Question 9

Describe transverse and longitudinal waves in terms of how they oscillate

Answer 9

transverse ways travel up and down perpendicular to the direction of travel.

longitudinal waves that have oscillations parallel to the direction of travel.

Question 10

Identify sound waves as
● longitudinal waves
● Describe how sound waves travel through a medium

Answer 10

Sound waves are longitudinal waves. Sound travels through a medium by making particles vibrate. They need a medium because it needs the vibration of particles. Therefore sound cannot travel through a vacuum.

Question 11

Link the frequency and amplitude of sound waves to the observed pitch and volume of sound.

Answer 11

the higher the amplitude the louder the sound

the pitch is the amount of waves that pass a point per second, more frequent the higher the pitch

Question 12

the law of reflection

Answer 12

The angle of incidence equals the angle of reflection

Question 13

Explain how the structures of the eye enable us to see (Cornea, lens, pupil, iris, retina, optic nerve)

Answer 13

Thick protective layer on the outside of the eye
Small hole that allows light to enter the eye
Coloured part of the eye that expands or shrinks to control the size of the pupil and controls the amount of light entering the eye.
Convex lens that refracts and converges light and focuses the image on the retina.
Special cells on the back of the eye that receive light and turn it into electrical signals
Transmit the signals from the retina to the brain

Question 14

Explain how changes of state occur in terms of energy and attraction between particles

Answer 14

When energy is added or removed a change of state can occur. As a substance is heated, the particles inside gain more energy and eventually when they have enough energy to overcome the
attractive forces between the particles the substance will change up a state. Conversely as a substance is cooled the particles lose energy and eventually when they have lost enough energy, the particles can no longer overcome the attractive forces and the substance changes down a state.

Question 15

Explain how matter can expand and contract

Answer 15

When a substance is heated the particles inside gain more kinetic energy and
start to vibrate/move more, this causes the particles to push against each other
more and spread apart. This causes the substance to expand.

Question 16

define density

Answer 16

Density measures how close together particles in a substance are. The higher the density the closer together the particles are.

Question 17

explain how the density of matter changes during expansion and contraction

Answer 17

As an object is heated it expands and its density decreases. This is because the mass of the object
stays the same but the volume of the object increases.
As an object is cooled it contracts and its density increases. This is because the mass of the object
stays the same but the volume of the object decreases.

Question 18

Describe the structure of an atom and state the electron configuration
of an atom

Answer 18

Every atom is made up of 3 subatomic particles: protons, neutrons and electrons. Protons and
neutrons exist in the nucleus while electrons exist in shells that orbit the nucleus. The outermost shell with electrons in it is called the
valence shell (electron shell).

Question 19

Explain why atoms are neutral overall

Answer 19

Neutrons have no charge and therefore do not affect the charge of the atom.
Protons have a positive charge whereas electrons have a negative charge; in an atom there are the
same number of protons and electrons.
The opposite charges of the protons and electrons cancel each other out and therefore the atom is
overall neutral.

Question 20

Identify the solvent and solute for a solution

Answer 20

A solution is when a solid has been dissolved in a liquid. The solid being dissolved is known as the
solute while the liquid the solid is being dissolved in is called the solvent. E.g. when making a cup
of coffee the coffee powder is the solute, the hot water is the solvent and when they are mixed
together they form a solution.

Question 21

Define concentration, dilute, concentrated, saturated

Answer 21

Concentration The amount of particles in a given volume.
Dilute A solution with a small amount of solute dissolved in a given volume of solvent.
Concentrated A solution with a large number of solute in a given volume of solvent.
Saturated A solution that cannot dissolve any more solute.

Question 22

Compare a dilute, concentrated and saturated solution

Answer 22

The terms dilute, concentrated and saturated refer to the amount of solute (dissolved solid) present
in the solution.

Question 23

Describe the seven life processes - MRS GREN

Answer 23

movement: Organism changes position of their body e.g to catch prey
Reproduction: To produce offspring to continue the species
Sensitivity: Sensing the environment e.g touch, taste, sight etc
Growth: Increasing cell size and number (organism gets bigger)
Respiration: Break down of glucose to produce energy
Excretion: Removing waste from the organism e.g carbon dioxide
Nutrition: Plants photosynthesising, animals consuming other organisms

Question 24

Classify things as living or non-living using MRS GREN

Answer 24

All organisms (bacteria, fungi, plants and animals) on Earth are considered living things
because they carry out the seven life processes - MRS GREN e.g plants move by growing
towards the light etc.
Viruses are non-living because the only life process they carry out is replication where they
have to use their host to copy themselves so it is not true reproduction. Fire, clouds, rocks
etc are also non-living because they do not carry out MRS GREN.

Question 25

Describe the term adaptation

Answer 25

An adaptation is an inherited trait/feature of an organism that enables it to survive in a specific environment

Question 26

Understand the roles of each type of organism in a food chain

Answer 26

Food chains are a diagram to show the flow of energy between organisms in a habitat. Food chains always start with a producer (plant) that photosynthesizes. Photosynthesis turns light energy into chemical potential energy for all the other organisms. Next is the primary consumer (herbivore); that eats the plant gaining the
energy it has stored. Following the primary consumer is the secondary consumer (a carnivore) which eats the primary consumer. A food chain can have a tertiary consumer (top predator). Another label used is trophic level (feeding level), the producer is the 1st trophic level, the herbivore is the 2nd trophic level.

Question 27

Discuss the reasons why Aotearoa has unique species

Answer 27

Aotearoa has been isolated from other land masses for around 80 million years. This means that Aotearoa had a unique set of conditions for organisms to adapt to. Almost no animals are able reach New
Zealand resulting in relatively unique species. New Zealand has so many flightless bird species because the birds have taken the place of ‘missing’ mammals on the ground as there were no predators to avoid and eat them or
their eggs.

Question 28

Discuss the reasons why a large number of Aotearoa animals and plants are vulnerable to extinction

Answer 28

In recent history the arrival of humans and the pests (mammals like rats, possums, cats) that
they have brought with them have changed those conditions by introducing more predators, more competition and bringing some endemic species to the brink of extinction. This has meant that the endemic species of New Zealand are less able to compete successfully.
Behavioral adaptations of endemic species (such as the freeze response/standing still)
reduce predation from traditional Aotearoa aerial predators e.g hawks. However, introduction
of land predators such as cats, possums and rats are still able to see and hunt animals that use the freeze response. This reduces the survival of the endemic species. Deforestation (chopping down trees) also reduces habitats for animals e.g. birds. Humans have hunted some animals to extinction, such as the Moa. Removal of species such as the Moa reduces the food available for the trophic level above it e.g. the Haast’s
Eagle that depended on the Moa for survival was no longer able to get the food it required and over time was less able to survive and reproduce as successfully, reduced in population and eventually became extinct. The extinction of these species reduced the biodiversity of Aotearoa.

Question 29

population growth curve of bacteria

Answer 29

It is exponential growth curve. It occurs when bacteria are in ideal
conditions (warmth, enough food, moisture, space)
Exponential growth does not continue indefinitely because:

● Food runs out
● Space runs out
● Toxic waste products build up

Question 30

Define the term pathogen

Answer 30

A pathogen is a disease causing microorganism.

Question 31

Discuss how bacteria have become resistant to antibiotics

Answer 31

Resistant strains can develop when people don’t finish the full course of antibiotics the doctor has prescribed. When you don’t finish the full course the antibiotics kills the weak bacteria and the stronger bacteria with more resistant genes survive to reproduce and take over

Question 32

outline the role of antibiotics

Answer 32

Antibiotics are chemicals produced by fungi that inhibit the reproduction and growth of bacteria. They have NO known effect on viruses and should never be taken to treat the symptoms of a cold or the ‘flu.
One antibiotic may only work against one type of bacteria, or a few types. This means that
different antibiotics are needed for the treatment of a range of bacterial diseases.

Question 33

Explain how bacterial food poisoning occurs and link this to the importance of
food safety

Answer 33

Bacterial food poisoning happens when food is contaminated with harmful bacteria and pathogens. These bacteria can grow in food if it’s improperly cooked or when food has gone over the expiry date. This is why you need to store raw food away from other foods so they don’t cross contaminate the raw meat juices. Food must be stored at the correct temperatures to prevent microbes multiplying and toxins building up.